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Diagnostic Accuracy of a Hand-Held Ultrasound Scanner in Routine Patients Referred for Echocardiography
CLINICAL INVESTIGATIONS ECHOCARDIOGRAPHY AT THE ‘‘POINT OF CARE’’
Diagnostic Accuracy of a Hand-Held Ultrasound Scanner in Routine Patients Referred for Echocardiography Christian Prinz, MD, and Jens-Uwe Voigt, MD, Leuven, Belgium; and Bad Oeynhausen, Germany
Background: The aim of this study was to investigate the imaging capabilities of recent hand-held ultrasound scanners. Methods: Three hundred forty-nine patients were scanned with hand-held ultrasound (HAND) and high-end echocardiography (HIGH). Segmental endocardial border delineation was scored (2 = good, 1 = poor, 0 = invisible) to describe image quality. Assessments of left ventricular (LV) dimensions, regional and global LV function, and grades of valve disease were compared. Results: The mean endocardial visibility grades were 1.6 6 0.5 with HAND and 1.7 6 0.4 with HIGH (P < .01). Regional wall motion was scored very similarly (k = 0.73, P < .01). Ejection fraction assessment (bias = 1.8%, 1.96 SD = 8.3%) and LV measurements (r = 0.99, P < .01; interventricular septum: bias = 0.91 mm, 1.96 SD = 2.1 mm; LV end-diastolic diameter: bias = 0.5 mm, 1.96 SD = 4.1 mm; LV posterior wall: bias = 0.61 mm, 1.96 SD = 2.4 mm) showed negligible deviations. No pericardial effusion or valve stenosis was missed. Regurgitations missed by HAND were all graded ‘‘minimal’’ on HIGH. Regurgitations were mildly overestimated by HAND. Overall concordance for detection of regurgitations was very good (k = 0.9, P < .01). Conclusions: Handheld echocardiography was feasible and missed no relevant findings. Given the future implementation of spectral Doppler capabilities, this handheld scanner can safely be used in clinical routine. (J Am Soc Echocardiogr 2011;24:111-6.) Keywords: Hand-held ultrasound scanner, Echocardiography, Image quality, Vscan
Since its introduction by Edler and Hertz1 in 1954, echocardiography has become an indispensable diagnostic tool in cardiac care. However, ultrasound machines were once large and heavy, limiting their easy use at the bedside.2,3 Early portable machines were heavy, had limited functionality and image quality, and were shown to miss important clinical findings.4 The recent introduction of handheld ultrasound (HAND) scanners the size of mobile phones allows these devices for the first time to be carried in one’s white coat, facilitating true bedside routine use. (Note that previous publications have used inconsistent terms for smaller echocardiographic machines. In this paper, we use the term hand-held for pocket scanners the size of mobile phones and the term portable for all other hand-carried devices.) However, concerns about image quality remain. Therefore, we investigated the feasibility and imaging From the Department of Cardiology, University Hospital Gasthuisberg, Catholic University Leuven, Leuven, Belgium (C.P., J.-U.V.) and the Department of Cardiology, Heart-Centre North Rhine-Westphalia, Ruhr-University Bochum, Bad Oeynhausen, Germany (C.P.). Reprint requests: Jens-Uwe Voigt, MD, Department of Cardiology, University Hospital Gasthuisberg, Catholic University Leuven, Herestraat 49, 3000 Leuven, Belgium (E-mail: [email protected]). 0894-7317/$36.00 Copyright 2011 by the American Society of Echocardiography. doi:10.1016/j.echo.2010.10.017
capabilities of the most recent and most advanced representative of this class of devices in comparison with contemporary high-end echocardiography (HIGH).
METHODS Study Population and Echocardiographic Protocol During a 5-week period, 349 unselected consecutive routine patients from the echocardiography lab at University Hospital Gasthuisberg (Leuven, Belgium) were scanned with a HAND scanner (Vscan; GE Vingmed Ultrasound AS, Horten, Norway; Figures 1A and 1B) and modern HIGH scanners, such as Vivid 7 or E9 (GE Vingmed Ultrasound AS) as the gold standard (using the M3S probe [GE Vingmed Ultrasound AS] at 1.5–4.0 MHz). Harmonic imaging was used in HIGH scanners by default. The examinations with HAND were performed by an experienced cardiologist after informed consent was obtained, directly before or after the regular echocardiographic examination with the HIGH scanner, which was performed independently by an experienced echocardiographer. Each examiner was blinded to the results of the other examination. Grayscale and color Doppler recordings from both scanners (apical four-chamber, threechamber, and two-chamber and parasternal long-axis and short-axis views) were digitally stored for further offline assessment. Feasibility and handling issues were documented after each examination. 111
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Abbreviations
EF = Ejection fraction HAND = Handheld ultrasound HIGH = High-end echocardiography LV = Left ventricular
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During offline analysis, images were read from a regular computer display using dedicated software. Image size was slightly bigger than on the device, but image resolution was identical. A single echocardiographer reviewed offline HAND and HIGH examinations of all subjects separately and in changing order, completely blinded to results of previous readings.
Specification and Capabilities of the HAND Device The display unit of the Vscan measures 135 73 28 mm. The probe measures 120 33 26 mm. The device and probe together weigh 390 g. The portrait-oriented (3:4) display has a diagonal dimension of 3.5 in (8.9 cm), with a resolution of 240 320 pixels. The displayed image sector for black and white imaging is 75 , with a maximum depth of 25 cm. The device offers regular gryascale imaging and color blood flow mode. The color flow box has a fixed size but can be moved with cursor keys. The bandwidth of the phasedarray probe is 1.7 to 3.8 MHz. The gain is adjusted automatically for all depths. The device offers an image based ‘‘Auto-Cycle’’ function for the automatic detection of a full heart cycle beginning with end-diastole. If this detection fails, a 2-second loop is stored. Distance measurements can be performed during an examination. The minimalistic keyboard contains only eight buttons. Voice recording is used for patient identification. Stills, image loops, and voice recordings are stored on a 4-GB micro-SD memory card in MP4 format and can be copied to a PC via the included docking station or directly from the card.
Data Analysis For analysis, HIGH data were transferred to a PC running EchoPAC software (GE Vingmed Ultrasound AS). Data from the HAND scanner were also transferred to a PC and reviewed using the dedicated Vscan Gateway software. Data analysis was performed in random order by an experienced cardiologist blinded to any patient data. A score for segmental endocardial border delineation was used to describe image quality in all recordings, as follows: 2 = good, 1 = poor, and 0 = not possible. Standard measurements of left ventricular (LV) dimensions (interventricular septal diameter, LV end-diastolic diameter, and LV posterior wall diameter) as well as visual assessment of regional (segmental wall motion score: 1 = normokinesia, 2 = hypokinesia, 3 = akinesia) and global (visually estimated ejection fraction [EF]) LV function were compared between HAND and HIGH. In both HAND and HIGH readings, EF was visually assessed using prespecified levels in intervals of 5%.The severity of valve regurgitation (0 = none, 1 = minimal, 2 = mild, 3 = moderate, 4 = severe) was graded according to cardiac morphology and the visual interpretation of the color Doppler jet. On the HIGH readings, the severity of a valve stenosis (0 = none, 1 = mild, 2 = moderate, 3 = severe) was evaluated using standard methods of routine echocardiography, such as pressure gradients and opening area calculation by continuity equitation or pressure half-time. On HAND readings, grading of valve stenosis was based on the interpretation of the available grayscale (chamber hypertrophy, valve calcification, and mobility) and color Doppler information (turbulence). The assessments were compared between machines.
Figure 1 The Vscan HAND device. Statistical Analysis Continuous data are expressed as mean 6 SD. Statistical analyses were performed using PASW (SPSS, Inc., Chicago, IL). For continuous and normally distributed data, paired t tests were used, and for nonnormally distributed data, Wilcoxon’s signed-rank tests were used. A two-tailed P value < .05 was considered significant. Continuous measurements were compared using Spearman’s correlation and Bland-Altman analysis. To determine the level of agreement between grades, we used weighted k statistics. Kappa values < 0.2 were interpreted as slight, 0.21 to 0.4 as fair, 0.41 to 0.6 as moderate, 0.61 to 0.8 as substantial, and 0.81 to 1.00 as very good agreement.5 RESULTS Patient Population We examined 349 consecutive routine patients (196 men). The mean age was 61.5 6 15.0 years (range, 20.0–89.0 years). The patients had a mean body mass index of 25.8 6 4.7 kg/m2 (range, 15.0–48.0 kg/m2). The LV EF ranged from 20% to 70% (mean, 55.6 6 10.0%). Use of the HAND Device Operating the device was easy and intuitive. Basic functions were found quickly by trial and error. After reading an A4-size instruction card, all functions could be controlled without problems. Lifting the screen switches the device on and initiates a new examination. We measured a booting time of 25 seconds. Voice recordings are used to identify the patient. The rechargeable battery allowed approximately 70 minutes of work. The time to recharge the battery was about 2 hours. For proper data storage without electrocardiographic triggering, the device relies on detecting cardiac cycles on the basis of the cyclic changes in the image. This algorithm works rather robustly and failed in 8.2% of all cases, leading to a sometimes disturbed image sequence. Image Quality The segmental visibility of the endocardium was graded with mean scores of 1.6 6 0.5 per patient with HAND and 1.7 6
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Figure 2 Comparison of image quality of the HAND device (top) and a HIGH device (bottom). (A) Echogenic patient. (B) Patient with suboptimal echogenicity. (C) Patient with bad echogenicity. (D) Patient with pericardial effusion. The pathology is somewhat more easily detected with the wider image sector of the HIGH device.
Figure 3 (Left) A good correlation (r = 0.91, P < .01) was found between readings with both types of devices. (Right) Bland-Altman plot shows no relevant bias and a normal variation of assessments. Data points of several patients are clustered because of the EF assessment in prespecified levels of 5%. 0.4 with HIGH as the gold standard (P < .01). In both echogenic and more difficult to scan patients, image quality was comparable. Only in patients with very bad echogenicity did HIGH tend toward advantageously better image quality (Figures 2A–2C). No frame rate information is provided on the display of the device. Analysis of the stored image loops revealed a constant frame rate of 20 frames/sec independent of depth settings for grayscale image loops and 13.6 frames/ sec in color Doppler mode.
bias (1.8%) and a normal variation (1.96 SD = 8.3%) (Figure 3). Regional wall motion was scored similarly on HAND and HIGH readings (k = 0.73, P < .01; Table 1).
Functional Assessment Visual EF estimates from HAND and HIGH image data correlated well (r = 0.91, P < .01). Bland-Altman analysis revealed no relevant
Detection of Pericardial Effusion Six study patients (1.7%) had pericardial effusions, which were detected equally with both devices (Figure 2D).
Dimensions LV measurements on HIGH and HAND image data correlated very well (r = 0.99, P < .01). Bland-Altman analysis showed no relevant bias or scatter (interventricular septum: bias = 0.91 mm, 1.96 SD = 2.1 mm; LV end-diastolic diameter: bias = 0.5 mm, 1.96 SD = 4.1 mm, LV posterior wall: bias = 0.61 mm, 1.96 SD = 2.4 mm; Figure 4).
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Table 1 Grading* of segmental wall motion (n = 6,175 segments) with the HAND device and the HIGH scanner HIGH scanner
HAND device (Vscan) NG 1 2 3
NG
1
2
3
6 3 0 0
119 5614 44 11
6 4 244 36
2 0 16 70
*NG, Not gradable; 1, normokinesia; 2, hypokinesia; 3, akinesia.
Regurgitant Lesions The device’s color Doppler mode is an advantage over earlier pocket echocardiographs, which did not provide this feature (Figure 2E). The relatively low frame rate is compensated for by high sensitivity, so that the color Doppler performs well when screening valve lesions in clinical practice. Using HIGH as the gold standard, a total of 330 patients with mitral regurgitation were detected, and nine mild mitral regurgitations were missed on HAND readings (2.6%). One mild mitral regurgitation was detected with HAND only (0.3%). The overall concordance for the detection of mitral regurgitations was substantial (k = 0.80, P < .01). Among 128 patients with aortic regurgitation on HIGH readings, eight (6.3%) were missed on HAND readings. Two regurgitations were detected only by HAND. The concordance for aortic regurgitations was very good (k = 0.94, P < .01). Tricuspid regurgitation was observed in 324 patients with HIGH and in 291 patients (89.8%) with HAND, resulting in moderate concordance (k = 0.6, P < .01; Table 2). The severity of mitral regurgitation was graded 1.4 6 0.8 on HAND readings and 1.3 6 0.6 on HIGH readings (P = .08), resulting in moderate agreement (k = 0.60, P < .01). The mean severity of aortic regurgitations was 1.5 6 0.8 with HAND and 1.3 6 0.6 with HIGH) (P = .10), with fair agreement (k = 0.40, P < .01). Mean tricuspid regurgitation was 1.3 6 0.9 with HAND and 1.3 6 0.6 with HIGH (P = .07), with moderate agreement (k = 0.44, P < .01; Figure 5). Overall concordance for the detection of regurgitations was very good (k = 0.90, P < .01). Grades of regurgitation severity differed by more than two grades between HAND and HIGH readings in only 1% of the cases. Stenotic Lesions Twenty-one patients (6%) had aortic stenoses. Despite lacking spectral Doppler, no stenosis was missed (k = 1.00, P < .01). The attempt to grade stenotic lesions with HAND was based on grayscale (visual estimation of valve opening) and color Doppler images due to color changes and the visual evaluation of flow velocity. This led to a relevant difference to the HIGH readings (k = 0.21, P > .05). In 11 patients, the severity of aortic stenosis was graded similarly on HAND and HIGH readings, while it underestimated by HAND readings in 10 patients (48%) (Figure 6).
DISCUSSION The introduction of HAND scanners has raised several questions. It is particularly interesting whether their image quality is sufficient for
clinical decision making in daily clinical practice, considering that earlier studies reported drawbacks of older portable ultrasound devices in a cardiology outpatient clinic,6 in cardiology consultations in a hospital setting,7 in the screening of special patient subsets,8 or in small unselected populations of a tertiary cardiac center.8-11 The few conflicting clinical assessments of the new HAND machines10,11 and the lack of data regarding their latest versions encouraged us to perform this study. Use of HAND The quality of the provided display is good. The handling of the device was very intuitive. Buttons could be mechanically more precise to avoid contact bounce. A booting time of 25 seconds seems too long for daily clinical practice. The battery capacity was appropriate, although time for recharging could be shorter. Image Quality, Functional Assessment, and Dimension Measurements Image quality appeared very good. The sector size of the image was appropriate but may need more attention for the detection of pericardial pathology (Figure 2). Despite the smaller sector width, it was possible to perform adequate imaging and quantitative assessment of even enlarged hearts in every case of our study population. The evaluation of regional wall motion, EF, and LV size was comparable. Because of the worse image quality in patients with very bad echogenicity, the overall image quality assessed by the visibility of the endocardium was slightly better with HIGH. Valve Lesions The detection of valve regurgitations demonstrated good concordance for mitral, aortic, and tricuspid regurgitations. The assessment of regurgitations tended to result in a slight overestimation of the lesion severity, but the overall accuracy was more than appropriate for the clinical use. In aortic stenosis, calcification and blood flow acceleration allowed the detection of a lesion. However, a correct quantification was impossible because of the lack of spectral Doppler, which led to an underestimation of stenosis severity in almost half the cases. Limitations All examinations in this study were performed by experienced investigators under optimal environmental light and patient positioning in the clinical routine echocardiography lab of the department. Therefore, we cannot comment on nonexpert use of handheld echocardiography. In particular, performance under more challenging conditions during bedside use4 was not tested, because the image quality comparison with HIGH scanners would have been impossible because of varying environmental conditions. Because of the small sector size and frame rate limitations of the HAND device, examinations should be performed with caution. High-end scanning will remain an indispensable part of good cardiologic practice, although the new HAND devices allow experienced echocardiographers to safely answer clinical questions within the scope of the devices’ capabilities. It appears unlikely and also not necessary that all features of a high-end ultrasound scanner will be implemented in such devices.
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Figure 4 Measurements of LV dimensions. (Left) Measurements from both types of devices correlated very well. (Right) Likewise, the Bland-Altman plot reveals no relevant bias and low variation between measurements.
Table 2 Detection of regurgitations HAND device (Vscan)
HIGH scanner Aortic regurgitation (n = 349) No Yes Tricuspid regurgitation (n = 349) No Yes Mitral regurgitation (n = 349) No Yes
No
Yes
219 2
8 120
25 33
0 291
18 9
1 321
Implications for Clinical Practice and the Health Care System Currently, there are no clinical trials or recommendations for the clinical use of HAND. The latest recommendations of the American Society of Echocardiography cover only the class of portable ultrasound.12 Although the performance of these expensive devices was either insufficient or the machines were too big and heavy for true bedside use, the new type of pocket-size scanner offering good image quality for less than the former price of an ultrasound probe raises political questions. Our study demonstrates, in general, excellent agreement between the image quality of the HAND and HIGH platforms when expert echocardiographers acquire and interpret images. We therefore conclude that quality and diagnostic accuracy of examinations within the given limitations of HAND devices depend on training and expertise rather than equipment. Conversely, this implies a potential danger of misdiagnosis by nonexpert users, which may become a common problem because of the low cost of HAND devices. To prevent this, medical authorities should adapt current reimbursement rules, and medical schools and echocardiographic societies should develop new educational concepts.13-15 When such devices include full standard echocardiographic functionality, including spectral Doppler, these questions will need to be answered.
Figure 5 Comparison of the grading of valve regurgitations with HAND (Vscan) and HIGH devices. For each valve, the sections of the bars indicate the percentage of patients in whom the severity of the regurgitation was graded equally in HAND and HIGH readings (green) or in whom HAND readings deviated by one (yellow) or two (orange) grades from HIGH readings. Disagreement of more than two grades did not occur.
In general, this new class of cardiac ultrasound scanners has the potential to introduce substantial changes in the way clinical cardiology is performed in routine clinical practice. The impact of these changes, however, must be the subject of further investigation.
CONCLUSIONS Echocardiography with handheld scanner was feasible in routine clinical practice. No clinically relevant findings were missed. Only spectral Doppler features are missing to make examinations complete and clinically valid. Apart from that, high-end scanning demonstrated advantages in image quality only in difficult-to-scan patients. Given the future implementation of full standard echocardiographic functionality, this new class of device has the potential to be safely used by experienced echocardiographers as diagnostic tool in routine clinical practice.
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Figure 6 Grading of aortic valve stenosis. Because of the lack of means of quantification (no spectral Doppler), the severity of aortic stenosis was frequently underestimated by visual analysis of HAND readings compared with HIGH readings (see ‘‘Methods’’ section for details). Importantly, however, no aortic stenosis was missed. Colors as in Figure 5. REFERENCES 1. Edler I, Hertz CH. The use of ultrasonic reflectoscope for the continuous recording of the movements of heart walls. Kungl Fysiografiska S€allskapets i Lund F€ orhandlingar 1954;24:40-58. 2. Ligtvoet C, Rijsterborgh H, Kappen L, Bom N. Real time ultrasonic imaging with a hand-held scanner. Part I—technical description. Ultrasound Med Biol 1978;4:91-2. 3. Roelandt JRTC, Wladimiroff JW, Baars AM. Ultrasonic real time imaging with a hand-held scanner. Part II—initial clinical experience. Ultrasound Med Biol 1978;4:93-7.
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4. Goodkin GM, Spevack DM, Tunick PA, Kronzon I. How useful is handcarried bedside echocardiography in critically ill patients? J Am Coll Cardiol 2001;37:2019-22. 5. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159-74. 6. Vourvouri EC, Poldermans D, de Sutter J, Sozzi B, Roelandt JRTC. Experience with an ultrasound stethoscope. J Am Soc Echocardiogr 2002;15: 80-5. 7. Greaves K, Jeetly P, Hickman M, Dwivedi G, Sabharwal N, Lim T, et al. The use of hand-carried ultrasound in the hospital setting—a cost-effectiveness analysis. J Am Soc Echocardiogr 2005;18:620-5. 8. Senior R, Galasko G, Hickman M, Jeetly P, Lahiri A. Community screening for left ventricular hypertrophy in patients with hypertension using handheld echocardiography. J Am Soc Echocardiogr 2004;17:56-61. 9. Vourvouri EC, Poldermans D, Schinkel AF, Koroleva LY, Sozzi FB, Parharidis GE, et al. Left ventricular hypertrophy screening using a hand-held ultrasound device. Eur Heart J 2002;26:1516-21. 10. Culp BC, Mock JD, Chiles CD, Culp WC. The pocket echocardiograph: validation and feasibility. Echocardiography 2010;27:759-64. 11. Egan M, Ionescu A. The pocket echocardiograph: a useful new tool? Eur J Echocardiogr 2008;9:721-5. 12. Seward JB, Douglas PS, Erbel R, Kerber RE, Kronzon I, Rakowski H, et al. Hand-carried cardiac ultrasound (HCU) device: recommendations regarding new technology. A report from the Echocardiography Task Force on New Technology of the Nomenclature and Standards Committee of the American Society of Echocardiography. J Am Soc Echocardiogr 2002; 15:369-73. 13. Zamorano JL, Moreno R, Alburquerque C. Echocardiography performed by physicians outside of echo-labs—is it possible? Eur Heart J 2002;23: 908-9. 14. Bruce CJ, Montgomery SC, Bailey KR, Tajik J, Seward JB. Utility of handcarried ultrasound devices used by cardiologists with and without significant echocardiographic experience in the cardiology inpatient and outpatient settings. Am J Cardiol 2002;90:1273-5. 15. Alexander JH, Peterson PD, Chen AY, Adams D, Kisslo JA. Feasibility of point of care echo by non-cardiologist physicians to assess left ventricular function, pericardial effusion, mitral regurgitation, and aortic valve thickening. Circulation 2001;104(suppl):334.
Diagnostic Accuracy of a Hand-Held Ultrasound Scanner in Routine Patients Referred for Echocardiography Christian Prinz, MD, and Jens-Uwe Voigt, MD, Leuven, Belgium; and Bad Oeynhausen, Germany
Background: The aim of this study was to investigate the imaging capabilities of recent hand-held ultrasound scanners. Methods: Three hundred forty-nine patients were scanned with hand-held ultrasound (HAND) and high-end echocardiography (HIGH). Segmental endocardial border delineation was scored (2 = good, 1 = poor, 0 = invisible) to describe image quality. Assessments of left ventricular (LV) dimensions, regional and global LV function, and grades of valve disease were compared. Results: The mean endocardial visibility grades were 1.6 6 0.5 with HAND and 1.7 6 0.4 with HIGH (P < .01). Regional wall motion was scored very similarly (k = 0.73, P < .01). Ejection fraction assessment (bias = 1.8%, 1.96 SD = 8.3%) and LV measurements (r = 0.99, P < .01; interventricular septum: bias = 0.91 mm, 1.96 SD = 2.1 mm; LV end-diastolic diameter: bias = 0.5 mm, 1.96 SD = 4.1 mm; LV posterior wall: bias = 0.61 mm, 1.96 SD = 2.4 mm) showed negligible deviations. No pericardial effusion or valve stenosis was missed. Regurgitations missed by HAND were all graded ‘‘minimal’’ on HIGH. Regurgitations were mildly overestimated by HAND. Overall concordance for detection of regurgitations was very good (k = 0.9, P < .01). Conclusions: Handheld echocardiography was feasible and missed no relevant findings. Given the future implementation of spectral Doppler capabilities, this handheld scanner can safely be used in clinical routine. (J Am Soc Echocardiogr 2011;24:111-6.) Keywords: Hand-held ultrasound scanner, Echocardiography, Image quality, Vscan
Since its introduction by Edler and Hertz1 in 1954, echocardiography has become an indispensable diagnostic tool in cardiac care. However, ultrasound machines were once large and heavy, limiting their easy use at the bedside.2,3 Early portable machines were heavy, had limited functionality and image quality, and were shown to miss important clinical findings.4 The recent introduction of handheld ultrasound (HAND) scanners the size of mobile phones allows these devices for the first time to be carried in one’s white coat, facilitating true bedside routine use. (Note that previous publications have used inconsistent terms for smaller echocardiographic machines. In this paper, we use the term hand-held for pocket scanners the size of mobile phones and the term portable for all other hand-carried devices.) However, concerns about image quality remain. Therefore, we investigated the feasibility and imaging From the Department of Cardiology, University Hospital Gasthuisberg, Catholic University Leuven, Leuven, Belgium (C.P., J.-U.V.) and the Department of Cardiology, Heart-Centre North Rhine-Westphalia, Ruhr-University Bochum, Bad Oeynhausen, Germany (C.P.). Reprint requests: Jens-Uwe Voigt, MD, Department of Cardiology, University Hospital Gasthuisberg, Catholic University Leuven, Herestraat 49, 3000 Leuven, Belgium (E-mail: [email protected]). 0894-7317/$36.00 Copyright 2011 by the American Society of Echocardiography. doi:10.1016/j.echo.2010.10.017
capabilities of the most recent and most advanced representative of this class of devices in comparison with contemporary high-end echocardiography (HIGH).
METHODS Study Population and Echocardiographic Protocol During a 5-week period, 349 unselected consecutive routine patients from the echocardiography lab at University Hospital Gasthuisberg (Leuven, Belgium) were scanned with a HAND scanner (Vscan; GE Vingmed Ultrasound AS, Horten, Norway; Figures 1A and 1B) and modern HIGH scanners, such as Vivid 7 or E9 (GE Vingmed Ultrasound AS) as the gold standard (using the M3S probe [GE Vingmed Ultrasound AS] at 1.5–4.0 MHz). Harmonic imaging was used in HIGH scanners by default. The examinations with HAND were performed by an experienced cardiologist after informed consent was obtained, directly before or after the regular echocardiographic examination with the HIGH scanner, which was performed independently by an experienced echocardiographer. Each examiner was blinded to the results of the other examination. Grayscale and color Doppler recordings from both scanners (apical four-chamber, threechamber, and two-chamber and parasternal long-axis and short-axis views) were digitally stored for further offline assessment. Feasibility and handling issues were documented after each examination. 111
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Abbreviations
EF = Ejection fraction HAND = Handheld ultrasound HIGH = High-end echocardiography LV = Left ventricular
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During offline analysis, images were read from a regular computer display using dedicated software. Image size was slightly bigger than on the device, but image resolution was identical. A single echocardiographer reviewed offline HAND and HIGH examinations of all subjects separately and in changing order, completely blinded to results of previous readings.
Specification and Capabilities of the HAND Device The display unit of the Vscan measures 135 73 28 mm. The probe measures 120 33 26 mm. The device and probe together weigh 390 g. The portrait-oriented (3:4) display has a diagonal dimension of 3.5 in (8.9 cm), with a resolution of 240 320 pixels. The displayed image sector for black and white imaging is 75 , with a maximum depth of 25 cm. The device offers regular gryascale imaging and color blood flow mode. The color flow box has a fixed size but can be moved with cursor keys. The bandwidth of the phasedarray probe is 1.7 to 3.8 MHz. The gain is adjusted automatically for all depths. The device offers an image based ‘‘Auto-Cycle’’ function for the automatic detection of a full heart cycle beginning with end-diastole. If this detection fails, a 2-second loop is stored. Distance measurements can be performed during an examination. The minimalistic keyboard contains only eight buttons. Voice recording is used for patient identification. Stills, image loops, and voice recordings are stored on a 4-GB micro-SD memory card in MP4 format and can be copied to a PC via the included docking station or directly from the card.
Data Analysis For analysis, HIGH data were transferred to a PC running EchoPAC software (GE Vingmed Ultrasound AS). Data from the HAND scanner were also transferred to a PC and reviewed using the dedicated Vscan Gateway software. Data analysis was performed in random order by an experienced cardiologist blinded to any patient data. A score for segmental endocardial border delineation was used to describe image quality in all recordings, as follows: 2 = good, 1 = poor, and 0 = not possible. Standard measurements of left ventricular (LV) dimensions (interventricular septal diameter, LV end-diastolic diameter, and LV posterior wall diameter) as well as visual assessment of regional (segmental wall motion score: 1 = normokinesia, 2 = hypokinesia, 3 = akinesia) and global (visually estimated ejection fraction [EF]) LV function were compared between HAND and HIGH. In both HAND and HIGH readings, EF was visually assessed using prespecified levels in intervals of 5%.The severity of valve regurgitation (0 = none, 1 = minimal, 2 = mild, 3 = moderate, 4 = severe) was graded according to cardiac morphology and the visual interpretation of the color Doppler jet. On the HIGH readings, the severity of a valve stenosis (0 = none, 1 = mild, 2 = moderate, 3 = severe) was evaluated using standard methods of routine echocardiography, such as pressure gradients and opening area calculation by continuity equitation or pressure half-time. On HAND readings, grading of valve stenosis was based on the interpretation of the available grayscale (chamber hypertrophy, valve calcification, and mobility) and color Doppler information (turbulence). The assessments were compared between machines.
Figure 1 The Vscan HAND device. Statistical Analysis Continuous data are expressed as mean 6 SD. Statistical analyses were performed using PASW (SPSS, Inc., Chicago, IL). For continuous and normally distributed data, paired t tests were used, and for nonnormally distributed data, Wilcoxon’s signed-rank tests were used. A two-tailed P value < .05 was considered significant. Continuous measurements were compared using Spearman’s correlation and Bland-Altman analysis. To determine the level of agreement between grades, we used weighted k statistics. Kappa values < 0.2 were interpreted as slight, 0.21 to 0.4 as fair, 0.41 to 0.6 as moderate, 0.61 to 0.8 as substantial, and 0.81 to 1.00 as very good agreement.5 RESULTS Patient Population We examined 349 consecutive routine patients (196 men). The mean age was 61.5 6 15.0 years (range, 20.0–89.0 years). The patients had a mean body mass index of 25.8 6 4.7 kg/m2 (range, 15.0–48.0 kg/m2). The LV EF ranged from 20% to 70% (mean, 55.6 6 10.0%). Use of the HAND Device Operating the device was easy and intuitive. Basic functions were found quickly by trial and error. After reading an A4-size instruction card, all functions could be controlled without problems. Lifting the screen switches the device on and initiates a new examination. We measured a booting time of 25 seconds. Voice recordings are used to identify the patient. The rechargeable battery allowed approximately 70 minutes of work. The time to recharge the battery was about 2 hours. For proper data storage without electrocardiographic triggering, the device relies on detecting cardiac cycles on the basis of the cyclic changes in the image. This algorithm works rather robustly and failed in 8.2% of all cases, leading to a sometimes disturbed image sequence. Image Quality The segmental visibility of the endocardium was graded with mean scores of 1.6 6 0.5 per patient with HAND and 1.7 6
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Figure 2 Comparison of image quality of the HAND device (top) and a HIGH device (bottom). (A) Echogenic patient. (B) Patient with suboptimal echogenicity. (C) Patient with bad echogenicity. (D) Patient with pericardial effusion. The pathology is somewhat more easily detected with the wider image sector of the HIGH device.
Figure 3 (Left) A good correlation (r = 0.91, P < .01) was found between readings with both types of devices. (Right) Bland-Altman plot shows no relevant bias and a normal variation of assessments. Data points of several patients are clustered because of the EF assessment in prespecified levels of 5%. 0.4 with HIGH as the gold standard (P < .01). In both echogenic and more difficult to scan patients, image quality was comparable. Only in patients with very bad echogenicity did HIGH tend toward advantageously better image quality (Figures 2A–2C). No frame rate information is provided on the display of the device. Analysis of the stored image loops revealed a constant frame rate of 20 frames/sec independent of depth settings for grayscale image loops and 13.6 frames/ sec in color Doppler mode.
bias (1.8%) and a normal variation (1.96 SD = 8.3%) (Figure 3). Regional wall motion was scored similarly on HAND and HIGH readings (k = 0.73, P < .01; Table 1).
Functional Assessment Visual EF estimates from HAND and HIGH image data correlated well (r = 0.91, P < .01). Bland-Altman analysis revealed no relevant
Detection of Pericardial Effusion Six study patients (1.7%) had pericardial effusions, which were detected equally with both devices (Figure 2D).
Dimensions LV measurements on HIGH and HAND image data correlated very well (r = 0.99, P < .01). Bland-Altman analysis showed no relevant bias or scatter (interventricular septum: bias = 0.91 mm, 1.96 SD = 2.1 mm; LV end-diastolic diameter: bias = 0.5 mm, 1.96 SD = 4.1 mm, LV posterior wall: bias = 0.61 mm, 1.96 SD = 2.4 mm; Figure 4).
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Table 1 Grading* of segmental wall motion (n = 6,175 segments) with the HAND device and the HIGH scanner HIGH scanner
HAND device (Vscan) NG 1 2 3
NG
1
2
3
6 3 0 0
119 5614 44 11
6 4 244 36
2 0 16 70
*NG, Not gradable; 1, normokinesia; 2, hypokinesia; 3, akinesia.
Regurgitant Lesions The device’s color Doppler mode is an advantage over earlier pocket echocardiographs, which did not provide this feature (Figure 2E). The relatively low frame rate is compensated for by high sensitivity, so that the color Doppler performs well when screening valve lesions in clinical practice. Using HIGH as the gold standard, a total of 330 patients with mitral regurgitation were detected, and nine mild mitral regurgitations were missed on HAND readings (2.6%). One mild mitral regurgitation was detected with HAND only (0.3%). The overall concordance for the detection of mitral regurgitations was substantial (k = 0.80, P < .01). Among 128 patients with aortic regurgitation on HIGH readings, eight (6.3%) were missed on HAND readings. Two regurgitations were detected only by HAND. The concordance for aortic regurgitations was very good (k = 0.94, P < .01). Tricuspid regurgitation was observed in 324 patients with HIGH and in 291 patients (89.8%) with HAND, resulting in moderate concordance (k = 0.6, P < .01; Table 2). The severity of mitral regurgitation was graded 1.4 6 0.8 on HAND readings and 1.3 6 0.6 on HIGH readings (P = .08), resulting in moderate agreement (k = 0.60, P < .01). The mean severity of aortic regurgitations was 1.5 6 0.8 with HAND and 1.3 6 0.6 with HIGH) (P = .10), with fair agreement (k = 0.40, P < .01). Mean tricuspid regurgitation was 1.3 6 0.9 with HAND and 1.3 6 0.6 with HIGH (P = .07), with moderate agreement (k = 0.44, P < .01; Figure 5). Overall concordance for the detection of regurgitations was very good (k = 0.90, P < .01). Grades of regurgitation severity differed by more than two grades between HAND and HIGH readings in only 1% of the cases. Stenotic Lesions Twenty-one patients (6%) had aortic stenoses. Despite lacking spectral Doppler, no stenosis was missed (k = 1.00, P < .01). The attempt to grade stenotic lesions with HAND was based on grayscale (visual estimation of valve opening) and color Doppler images due to color changes and the visual evaluation of flow velocity. This led to a relevant difference to the HIGH readings (k = 0.21, P > .05). In 11 patients, the severity of aortic stenosis was graded similarly on HAND and HIGH readings, while it underestimated by HAND readings in 10 patients (48%) (Figure 6).
DISCUSSION The introduction of HAND scanners has raised several questions. It is particularly interesting whether their image quality is sufficient for
clinical decision making in daily clinical practice, considering that earlier studies reported drawbacks of older portable ultrasound devices in a cardiology outpatient clinic,6 in cardiology consultations in a hospital setting,7 in the screening of special patient subsets,8 or in small unselected populations of a tertiary cardiac center.8-11 The few conflicting clinical assessments of the new HAND machines10,11 and the lack of data regarding their latest versions encouraged us to perform this study. Use of HAND The quality of the provided display is good. The handling of the device was very intuitive. Buttons could be mechanically more precise to avoid contact bounce. A booting time of 25 seconds seems too long for daily clinical practice. The battery capacity was appropriate, although time for recharging could be shorter. Image Quality, Functional Assessment, and Dimension Measurements Image quality appeared very good. The sector size of the image was appropriate but may need more attention for the detection of pericardial pathology (Figure 2). Despite the smaller sector width, it was possible to perform adequate imaging and quantitative assessment of even enlarged hearts in every case of our study population. The evaluation of regional wall motion, EF, and LV size was comparable. Because of the worse image quality in patients with very bad echogenicity, the overall image quality assessed by the visibility of the endocardium was slightly better with HIGH. Valve Lesions The detection of valve regurgitations demonstrated good concordance for mitral, aortic, and tricuspid regurgitations. The assessment of regurgitations tended to result in a slight overestimation of the lesion severity, but the overall accuracy was more than appropriate for the clinical use. In aortic stenosis, calcification and blood flow acceleration allowed the detection of a lesion. However, a correct quantification was impossible because of the lack of spectral Doppler, which led to an underestimation of stenosis severity in almost half the cases. Limitations All examinations in this study were performed by experienced investigators under optimal environmental light and patient positioning in the clinical routine echocardiography lab of the department. Therefore, we cannot comment on nonexpert use of handheld echocardiography. In particular, performance under more challenging conditions during bedside use4 was not tested, because the image quality comparison with HIGH scanners would have been impossible because of varying environmental conditions. Because of the small sector size and frame rate limitations of the HAND device, examinations should be performed with caution. High-end scanning will remain an indispensable part of good cardiologic practice, although the new HAND devices allow experienced echocardiographers to safely answer clinical questions within the scope of the devices’ capabilities. It appears unlikely and also not necessary that all features of a high-end ultrasound scanner will be implemented in such devices.
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Figure 4 Measurements of LV dimensions. (Left) Measurements from both types of devices correlated very well. (Right) Likewise, the Bland-Altman plot reveals no relevant bias and low variation between measurements.
Table 2 Detection of regurgitations HAND device (Vscan)
HIGH scanner Aortic regurgitation (n = 349) No Yes Tricuspid regurgitation (n = 349) No Yes Mitral regurgitation (n = 349) No Yes
No
Yes
219 2
8 120
25 33
0 291
18 9
1 321
Implications for Clinical Practice and the Health Care System Currently, there are no clinical trials or recommendations for the clinical use of HAND. The latest recommendations of the American Society of Echocardiography cover only the class of portable ultrasound.12 Although the performance of these expensive devices was either insufficient or the machines were too big and heavy for true bedside use, the new type of pocket-size scanner offering good image quality for less than the former price of an ultrasound probe raises political questions. Our study demonstrates, in general, excellent agreement between the image quality of the HAND and HIGH platforms when expert echocardiographers acquire and interpret images. We therefore conclude that quality and diagnostic accuracy of examinations within the given limitations of HAND devices depend on training and expertise rather than equipment. Conversely, this implies a potential danger of misdiagnosis by nonexpert users, which may become a common problem because of the low cost of HAND devices. To prevent this, medical authorities should adapt current reimbursement rules, and medical schools and echocardiographic societies should develop new educational concepts.13-15 When such devices include full standard echocardiographic functionality, including spectral Doppler, these questions will need to be answered.
Figure 5 Comparison of the grading of valve regurgitations with HAND (Vscan) and HIGH devices. For each valve, the sections of the bars indicate the percentage of patients in whom the severity of the regurgitation was graded equally in HAND and HIGH readings (green) or in whom HAND readings deviated by one (yellow) or two (orange) grades from HIGH readings. Disagreement of more than two grades did not occur.
In general, this new class of cardiac ultrasound scanners has the potential to introduce substantial changes in the way clinical cardiology is performed in routine clinical practice. The impact of these changes, however, must be the subject of further investigation.
CONCLUSIONS Echocardiography with handheld scanner was feasible in routine clinical practice. No clinically relevant findings were missed. Only spectral Doppler features are missing to make examinations complete and clinically valid. Apart from that, high-end scanning demonstrated advantages in image quality only in difficult-to-scan patients. Given the future implementation of full standard echocardiographic functionality, this new class of device has the potential to be safely used by experienced echocardiographers as diagnostic tool in routine clinical practice.
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Figure 6 Grading of aortic valve stenosis. Because of the lack of means of quantification (no spectral Doppler), the severity of aortic stenosis was frequently underestimated by visual analysis of HAND readings compared with HIGH readings (see ‘‘Methods’’ section for details). Importantly, however, no aortic stenosis was missed. Colors as in Figure 5. REFERENCES 1. Edler I, Hertz CH. The use of ultrasonic reflectoscope for the continuous recording of the movements of heart walls. Kungl Fysiografiska S€allskapets i Lund F€ orhandlingar 1954;24:40-58. 2. Ligtvoet C, Rijsterborgh H, Kappen L, Bom N. Real time ultrasonic imaging with a hand-held scanner. Part I—technical description. Ultrasound Med Biol 1978;4:91-2. 3. Roelandt JRTC, Wladimiroff JW, Baars AM. Ultrasonic real time imaging with a hand-held scanner. Part II—initial clinical experience. Ultrasound Med Biol 1978;4:93-7.
Journal of the American Society of Echocardiography February 2011
4. Goodkin GM, Spevack DM, Tunick PA, Kronzon I. How useful is handcarried bedside echocardiography in critically ill patients? J Am Coll Cardiol 2001;37:2019-22. 5. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159-74. 6. Vourvouri EC, Poldermans D, de Sutter J, Sozzi B, Roelandt JRTC. Experience with an ultrasound stethoscope. J Am Soc Echocardiogr 2002;15: 80-5. 7. Greaves K, Jeetly P, Hickman M, Dwivedi G, Sabharwal N, Lim T, et al. The use of hand-carried ultrasound in the hospital setting—a cost-effectiveness analysis. J Am Soc Echocardiogr 2005;18:620-5. 8. Senior R, Galasko G, Hickman M, Jeetly P, Lahiri A. Community screening for left ventricular hypertrophy in patients with hypertension using handheld echocardiography. J Am Soc Echocardiogr 2004;17:56-61. 9. Vourvouri EC, Poldermans D, Schinkel AF, Koroleva LY, Sozzi FB, Parharidis GE, et al. Left ventricular hypertrophy screening using a hand-held ultrasound device. Eur Heart J 2002;26:1516-21. 10. Culp BC, Mock JD, Chiles CD, Culp WC. The pocket echocardiograph: validation and feasibility. Echocardiography 2010;27:759-64. 11. Egan M, Ionescu A. The pocket echocardiograph: a useful new tool? Eur J Echocardiogr 2008;9:721-5. 12. Seward JB, Douglas PS, Erbel R, Kerber RE, Kronzon I, Rakowski H, et al. Hand-carried cardiac ultrasound (HCU) device: recommendations regarding new technology. A report from the Echocardiography Task Force on New Technology of the Nomenclature and Standards Committee of the American Society of Echocardiography. J Am Soc Echocardiogr 2002; 15:369-73. 13. Zamorano JL, Moreno R, Alburquerque C. Echocardiography performed by physicians outside of echo-labs—is it possible? Eur Heart J 2002;23: 908-9. 14. Bruce CJ, Montgomery SC, Bailey KR, Tajik J, Seward JB. Utility of handcarried ultrasound devices used by cardiologists with and without significant echocardiographic experience in the cardiology inpatient and outpatient settings. Am J Cardiol 2002;90:1273-5. 15. Alexander JH, Peterson PD, Chen AY, Adams D, Kisslo JA. Feasibility of point of care echo by non-cardiologist physicians to assess left ventricular function, pericardial effusion, mitral regurgitation, and aortic valve thickening. Circulation 2001;104(suppl):334.